Workflow to convert rendered images to video
The only tool I've ever needed is ffmpeg. Here is my standard "recipe" for command-line conversion:

To convert default Blender sequenced PNGs at 24fps to a lossless 24fps YUV420p colorspace, x264 format video:

ffmpeg -r 24 -i %04d.png -c:v libx264 -r 24 -pix_fmt yuv420p -qp 0 output.mp4


The quality is determined by "-qp", with 0 best (lossless) quality, 51 worst. Also, know that the first "-r" determines how long each PNG will be shown, while the second "-r" determines the actual framerate of the output video. 

As an example using that same command above, but starting from 0100.png, with each image viewable for 5 seconds in a video with a framerate of 30fps, plus a forced-rescale to 1920x1080 thrown in too:

ffmpeg -r 1/5 -start_number 100 -i %04d.png -c:v libx264 -r 30 -s 1920x1080 -pix_fmt yuv420p -qp 0 output.mp4